The objective of the research is to elucidate the molecular basis for permeability and transport functions of cell membranes in general, and of the malignant cell membrane in particular. The role of membrane glycoproteins in solute transfer across the mouse Ehrlich ascites tumor cell will be studied, using lectins as membrane probes. Lectins are proteins of plant or invertebrate origin which bind to specific sugar groups of plasma membrane glycoproteins or glycolipids. The lectin, Concanavalin A, binds to membrane glycoprotein of the Ehrlich ascites cell and causes profound changes in cell cation content. The mechanism of these changes will be determined by measuring unidirectional as well as net fluxes. In addition, the transfer of glycine, 3-0-methyl-glucose, thiourea, and chloride will be studied. Comparative investigations using a variety of lectins with different sugar specificities and neuraminidase will allow a determination of the sugar moieties which are important in the transfer of different solutes. Other parameters of transport which will be determined are cell ATP content and Na-K-ATPase activity. Binding characteristics of the lectins will be studied under a number of conditions. Collaborative work with Dr. Martin Nachbar and Dr. Joel Oppenheim, who are identifying and purifying the lectin receptors of these cells, should make possible further characterization of the molecular units which influence and regulate permeability and transport. In addition, they will prepare antibodies to the purified receptors and these will be used to determine the association between the purified membrane constituents and specific transport mechanisms. It is hoped that this investigation will lead to a basic understanding of the tumor cell membrane and of the structural basis for specific functional membrane properties. BIBLIOGRAPHIC REFERENCES: Nachbar, Martin S., Joel D. Oppenheim, and Felice Aull. Interactions of lectins with plasma membrane glycoproteins of the Ehrlich ascites carcinoma cell. Biochim. Biophys. Acta. 419:512-529, 1976. Aull, F., M. S. Nachbar, and J. D. Oppenheim. Mechanism of lectin induced changes in potassium transport of Ehrlich ascites tumor cells. Fed. Proc. 35:605, 1976 (abstract).